The present invention relates generally to coating compositions and particularly to a polyester based thermosetting primer-surfacer composition having low volatile organic content.
Primer-surfacer compositions are employed in the automobile and truck manufacturing industry as one component of multicomponent vehicle finishes. In a typical vehicle finishing operation as presently practiced, an electrodeposited primer composition is applied to a metal substrate, which optionally can be pretreated by galvanizing or phosphatizing to impart corrosion resistance. A primer-surfacer composition is then applied over the electrodeposited primer, and serves to fill minor imperfections in the substrate and provide a smooth, even surface suitable for application of visible topcoats. Defects in the primer-surfacer layer are removed by sanding.
Following application of a primer-surfacer, a base coat of acrylic lacquer, acrylic dispersion, acrylic enamel, polyurethane enamel, alkyd enamel, or other pigmented coating composition is applied and cured. In most finish operations, a final layer of a clear coating composition is applied to enhance gloss, durability, and overall appearance of the resulting multicomponent vehicle finish.
Some typical sealer and primer compositions representative of the prior art in this area are disclosed by Barrett et al., U.S. Pat. No. 2,873,210, Swanson and Walus, U.S. Pat. No. 3,272,647, Jeffery et al., U.S. Pat. No. 3,505,269, Rohrbacher, U.S. Pat. No. 3,509,086, Sandstedt, U.S. Pat. No. 3,627,779, and Fanning, U. S. Pat. No. 4,042,539.
Use of a primer-surfacer composition which is color-keyed to the base coat enables better base coat coverage at given application levels, providing savings in material costs. In addition, more transparent base coats can be employed, which provide better appearance characteristics. Use of primer-surfacers having high gloss enables easier detection, and hence, correction, of surface imperfections during the finishing process.
New polyester-based flexible primer-surfacer compositions having excellent adhesion to metal and polymeric substrates, high solids, high gloss, and pigments for color keying are of significant interest to the automobile and truck manufacturing industries.